1. Field of the Invention
The present invention concerns antitumor compounds. More particularly, the invention provides novel paclitaxel derivatives, pharmaceutical formulations thereof, and their use as antitumor agents.
2. Background Art
Taxol.RTM. (paclitaxel) is a natural product extracted from the bark of Pacific yew trees, Taxus brevifolia. It has been shown to have excellent antitumor activity in in vivo animal models, and recent studies have elucidated its unique mode of action, which involves abnormal polymerization of tubulin and disruption of mitosis. It has recently been approved for the treatment of refractory advanced ovarian cancer and breast cancer; and studies involving other cancers have shown promising results. The results of paclitaxel clinical studies are reviewed by numerous authors, such as by Rowinsky and Donehower in "The Clinical Pharmacology and Use of Antimicrotubule Agents in Cancer Chemotherapeutics," Pharmac. Ther., 52:35-84, 1991; by Spencer and Faulds in "Paclitaxel, A Review of its Pharmacodynamic and Pharmacokinetic Properties and Therapeutic Potential in the Treatment of Cancer," Drugs, 48 (5) 794-847, 1994; by K. C. Nicolaou et al. in "Chemistry and Biology of Taxol," Angew. Chem., Int. Ed. Engl., 33: 15-44, 1994; by F. A. Holmes, A. P. Kudelka, J. J. Kavanaugh, M. H. Huber, J. A. Ajani, V. Valero in the book "Taxane Anticancer Agents Basic Science and Current Status" edited by Gunda I. Georg, Thomas T. Chen, Iwao Ojima, and Dolotrai M. Vyas, 1995, American Chemical Society, Washington, D.C., 31-57; by Susan G. Arbuck and Barbara Blaylock in the book "TAXOL.RTM. Science and Applications" edited by Mathew Suffness, 1995, CRC Press Inc., Boca Raton, Fla., 379-416; and also in the references cited therein.
A semi-synthetic analog of paclitaxel named Taxotere.RTM. (docetaxel) has also been found to have good antitumor activity. The structures of paclitaxel and Taxotere.RTM. are shown below along with the conventional numbering system for molecules belonging to the class; such numbering system is also employed in this application. ##STR1## Taxol.RTM.: R=Ph; R'=acetyl Taxotere.RTM.: R=t-butoxy; R'=hydrogen